The present invention relates to a bum per system containing a bumper running transverse to the longitudinal direction of a vehicle, a connecting element on the bumper for attaching the bumper to a vehicle, in particular onto the longitudinal beam of a passenger car, and attachment means for mounting a releasable towing facility. The connecting element is a multi-chamber extruded section of metal having a longitudinal axis (x) lying in the longitudinal direction of the vehicle. The connecting element is in the form of a safety element which under impact conditions absorbs impact energy by compressive deformation. The invention relates also to a process for manufacturing the bumper system according to the invention.
Bumper systems with the above mentioned structure are also required to protect the vehicle structure behind them from the impact energy acting on the vehicle when the impact is small. For that reason the connecting elements are often in the form of hollow, multi-chamber sections which on impact absorb energy in the longitudinal direction of the section by plastic deformation, in particular by a planned folding action. The bumper systems must therefore be easy to repair in order that these or individual components thereof e.g. bumper or connecting element can be replaced at relatively low cost after suffering impact.
Usually the bumper system also includes attachment means which enable the vehicle to be towed away when involved in an accident. As a rule these attachment means comprise a thread provided in the bumper system into which a towing hook can be screwed. In many types of vehicle the thread is provided in the bumper. The tensile force caused by the towing action is then transmitted via the bumper into the vehicle structure or frame.
Also known are bumper systems in which a threaded socket is welded at the side on the wall of the connecting element. The towing hook is then introduced through an opening in the bumper and screwed into the threaded socket. The advantage of this solution is that the tensile force acts directly on the connecting element and the bumper is not subjected to loading.
If the attachment means is mounted on the connecting element, then care should be taken that the energy absorbing properties of the connecting element are not impaired. This means that, in spite of this attachment means, the connecting element should exhibit optimum compression or folding behavior on collision.
In both cases, providing the bumper system with an attachment means for a towing hook involves considerable additional expense as the inner thread has to be created in separate working steps, often by hand e.g. by welding.